A feeding device for bulk material must transfer the bulk material from a storage bin into a feeding chute equipped with a vibratory drive unit. The chute discharges a fed amount by the vibratory conveying motion of the feeding chute.
In addition to fibrous material, such as glass fibers or carbon fibers, other materials and material compositions of various types are also known to be difficult to feed or to transport as bulk material along a chute vibrating longitudinally. Such products include chemical semi-finished products and finished products, cossettes, flakes, chips, shavings, and the like. With such types of bulk material it is often not possible to maintain a constant and even flow of material on conveyor equipment because such bulk material tends to bunch up or the conveyor unit becomes unevenly loaded because material gets caught or stuck, sticks together, etc. As a result, considerable difficulties often occur when such types of material are to be discharged from a conveyor device. This also applies to vibrating chutes, in which the bulk material is subjected to vibratory motions and is transported in a known manner by means of micro-throw-type motions.
It is known that, for feeding glass fibers, a loss-in-weight-system feeding or weighing scale is used, on which a storage bin for the glass fibers plus a conveyor or feeding chute are arranged. The conveyor or feeding chute discharges the bulk material from the storage bin. The discharge from the feeding chute is controlled in an open or closed loop manner with the aid of an output signal from the loss-in-weight-system or weighing scale.
Many different versions of loss-in-weight-systems or weighing scales for feeding bulk materials are known. Such scales usually comprise a storage bin plus a discharge mechanism, such as a feeding chute supported on a scale or on load cells. In the case of such feeding scales, the reduction in weight that occurs on the scale or on the load cells within a time unit serves to control, in a closed loop manner, the delivery of the bulk material to be fed, from the storage bin.
Since, in spite of the vibrating device, glass fibers do not distribute themselves evenly in the feeding chute, bunching and gaps in the material flow occur repeatedly, making it difficult to discharge the material evenly or to evenly feed the glass fibers. Because of this, attempts have been made to even out the flow of the glass fibers by using guide or distribution devices that dip down into the glass fibers from above. However, such attempts have been only partially successful in conventional devices.
U.S. Pat. No. 4,527,747 (Scharmer et al.) discloses a vibratory chute to which vibration forces are applied in such a manner that the goods passing through the chute tend to follow a helix type revolving motion. This motion is suitable to, for example, separate sand from cast elements. However, the uniform evenly fed transport of bulk materials such as glass fibers is not possible by the application of special forces to the chute. Applying special vibrating forces directly to the bulk material in the chute is not suggested by Scharmer et al.